Valve operating mechanism for engines



Oct. 10, 1939. J. D. TURLAY VALVE OPERATING MECHANISM FOR ENGINES FiledSept. 24, 1936 5 I fizz Patented Oct. 10, 1939 i UNITED STATES PATENTOFFICE VALVE OPERATING MECHANISM FOR ENGINES Joseph D. Turlay. Flint,Mich, assignor to General Motors Corporation, Detroit, Mich., acorporation of Delaware Application September 24, 1936, Serial No.102,328

3 Claims. (Cl. 123-90) This invention relates to a method of and theirexpansion will be a function of lubricant means for controlling thevalve lash or clearance temperature. As was stated previously, the oilin an internal combustion engine. temperature rise is considerablyslower than the In the operation of an internal combustion watertemperature rise which means that the dis- 5 engine the problem ofcontrolling valve lash or tance between the cam shaft and rocker arm 5clearance is a complicated one. If the valve lash shaft is rapidlyincreased due to the expansion of is adjusted for normal conditions ofoperation the cylinder block. The push rod on'the other there will be anexcessive clearance when starting hand receives a bath of cold oil fromthe crankcold. This excess clearance results in unpleasant case and itstemperature rise lags behind that of noise and tends to cause excessivewear of the the upper part of the engine. Under this condi- 10 severalparts due to the pounding action thereof. tion the push rod is too shortand there is an On the other hand if the clearance is reduced excess ofvalve lash with resultant noise. there may be insufficient clearance atmore ex- Under extreme driving conditions or in Warm treme operatingconditions so that the valves weather the antithesis of this situationwill exist.

will remain partially open and cause faulty oper- The oil temperaturewill rise above that of the 15 ation and burning and/or pitting of thevalves water. While the distance between the cam and the seats therefor.shaft and the rocker arm shaft will be increased To obtain satisfactoryengine performance as as compared with the distance when the enginequickly as possible after starting cold it is cusis cold the push rodwill be expanded a greater tomary to provide a thermostat which remainsamount and the push rods will become too long 20 closed until operatingtemperature is reached and and reduce the lash. forces the coolingmedium, such as water for The problem of valve lash is furthercompliexample, to recirculate through a bypass valve cated by anotherfactor, namely, the unequal cowithout passing through the radiator. Thecoolefficients of expansion of cast iron and steel.

ing medium usually surrounds the combustion Steel expands about 13% moreper degree rise in 25 chamber and cylinder wall and is rapidly heatedtemperature than does cast iron. It is customary to operatingtemperature even in the coldest to lash valves with the oil and watertemper- Weather from heat rejected from the engine. atures equal to thenormal temperature of the The engine lubricant, however, is heated muchwater. The push rods being of steel contract more slowly. The lubricantis carried in the botmore upon cooling than does the cylinder block 30tom of the engine away from the combustion zone. of cast iron andtherefore increases the valve Relatively small quantities thereof areallowed to lash several thousandths of an inch in cold come in contactwith the pistons and cylinder weather. The cumulative eifect of theseveral Walls. Hence, the time required for the lubricant factorsproduces excessive noise in the valve to reach even the normal watertemperature is mechanism during the warm up period. Various 5 severaltimes greater than the water itself. Under compensating means have beenused in the past, hard driving conditions or in warm weather the usuallyof a complicated nature. I have devised oil normally reaches a muchhigher operating a simple means for more effectively controllingtemperature than the water. Valve lash than devices used in the past.

The result of these two dissimilar temperature It is an object of myinvention to improve the 40 characteristics has a definite effect onvalve lash valve lash characteristics of an engine. or clearance andconsequently upon valve mecha- Another object of my invention is toprovide a nism noise. It is obvious that in order to mainnew andimproved method and means for contain a constant valve lash with achange in temtrolling the valve lash in an internal combustion isperature all units must expand or contract at an engine. equal rate. Astill further object of my invention is a new Consider the case of asimple correctly lashed and improved method and means for maintainvalvemechanism when the engine is started cold. ing more nearly constant thandevices used in The upper portion of the engine quickly warms up thepast the valve lash or clearance of an internal and expands which meansthat the distance becombustion engine throughout Widely variable tweenthe rocker arm shaft and the cam shaft conditions of operation.increases. The push rods are insulated from the It is also an object ofmy invention to provide cylinder block and thus do not respond rapidlyvalve mechanism in which noise is greatly reto changes in blocktemperature. In addition, the duced.

push rods receive a constant flow of oil and hence A specific object ofmy invention resides in a 5'5 new and improved rocker arm shaft supportformed of aluminum or alloys thereof.

Another object of my invention is a new method and means of controllingvalve lash involving regulation and control of the temperature of thelubricant for the push rod and expansion and contraction of rocker armsupports of different material than the engine block and push rods.

Other advantages and objects of my invention reside in the specificcombinations and arrangements of parts as will become more apparent asthe description proceeds.

Reference is herein made to the drawing forming a portion of thisspecification, in which:

Figure l is a side elevational view, with parts in section, of aninternal combustion engine in which my invention is incorporated.

Figure 2 is a view taken substantially on line 2--2 in Figure 1; and

Figure 3 is an enlarged detail view taken on line 3-3 in Figure 1.

In the drawing, I is a piston adapted to reciprocate in cylinder 3.Spaced walls 2 and 4 form a passage 5 for cooling water or other mediumto surround and cool piston I. Cylinder head member 6, having passagesI, 8 and 9 for cooling water or other cooling medium, is adapted to formwith the cylinder 3 a combustion chamber l0.

Valve ll having a spring 12 between a support 13 on the cylinder headand a disc-like member I4 fixed to the upper end of the valve stem isadapted to close the valve against seat l5. By means of camshaft l6having cam ll thereon, cam follower [8, push rod l9, and rocker arm 20the valve is caused to open against the force of spring l2 at timedintervals in the cycle of operation as will be readily understood.

A hollow rocker arm shaft 2| is supported from the upper face of thecylinder head by means of supports 22 formed of aluminum or alloysthereof. The supports 22 are fixed to the head by means of members 30.Preferably the suports are of aluminum alloy die castings in place ofthe malleable iron or ferrous metal supports commonly employed. Thecoefficient of expansion of aluminum is more than twice that of castiron and this property is utilized, for controlling the valve lash aswill later become apparent.

Within and spaced from the inner walls of the shaft 2| is a tubularmember 23 within which the cooling medium is caused to circulate bymeans of pump 24. Lubricating oil is forced by means of pump 25, pipeline 26 into space 2'1 between tube 23 and the inside of shaft 2|. Asshown in Figure 1, oil is forced into the space 21 at a pointsubstantially midway between the ends of the rocker arm shaft. The oilwill flow toward both ends of the rocker arm shaft and lubricate theseveral rocker arm bearings and push rods, oil passageway 28 permittingoil to reach the push rods. The Water within tubular member 23 willregulate the oil temperature by heating a portion of the oil during thewarming up period and cooling a portion thereof during extreme operatingconditions. It will be understood that there may be any desired numberof cylinders, pistons, valves, valve rocker arms and push rods.

By means of the construction described above the valve lash may be heldwithin narrow limits. If now the engine be lashed as previouslydescribed with the oil and water temperatures equal to the normal watertemperature the aluminum brackets will have expanded considerably inlength from that of the cold condition thereof.

Upon a cooling of the several parts as by standing over night thebrackets will contract approximately twice as much as would the sameelements if formed of ferrous metal. Accordingly the contraction of thealuminum or aluminum alloy rocker arm support will be approximatelytwice as much or more than the ferrous metals used for the push rod orcylinder block and thereby decrease the valve stem clearance severalthousandths of an inch under that of normal hot lash. Now since this isso, a certain amount of expansion of the cylinder block due to quickwater temperature rise during warm up is possible before the lashreaches even its nominal value.

The temperature of the rocker arm supports is controlled in part by thewater and in part by the oil flowing through the rocker arm shaft. Thecombined effect is something of a mean between the expansion expected ifeither factor predominated. However, their action is such that themaximum lash encountered during the warming up period is considerablyunder that obtained with malleable iron or other ferrous metal supports,thus appreciably reducing noise and wear of the several parts.

In the case of very hot oil under extreme operating conditions thealuminum or aluminum alloy supports expand greatly and maintainsufficient clearance by compensating for the increase in length of thesteel push rods and valve stems.

Under extreme conditions of operation the portion of the hot oil whichflows in contact with tubular member 23 containing the cooling mediumwill be cooled. The cooled portion flows to the push rods and they willremain cooler than would otherwise be the case.

It will be apparent that I have provided a simple and convenient meansfor controlling valve lash and valve mechanism noise.

Although I have shown and described one specific construction, form andarrangement of parts as illustrative of an embodiment of my invention,various changes may be made therein without departing from the spirit ofmy invention and I do not wish to limit the patent granted thereon otherthan as necessitated by the prior art.

I claim:

1. Mechanism for controlling valve lash in an internal combustion enginewhich comprises, a valve rocker arm, a rocker arm shaft, a push rod,means for maintaining the push rod cooler than the normal cooling mediumtemperature during the warming up period and hotter than the coolingmedium under severe conditions of operation and means for supportingsaid rocker arm shaft, said last mentioned means constituting the solesupporting means for said shaft and being formed wholly of a materialhaving a substantially greater coefficient of expansion than the otherparts.

2. Mechanism for controlling valve lash in an internal combustion enginewhich comprises, a valve, a valve rocker arm, a valve rocker arm shaft,a push rod for operating the valve rocker arm, means for maintaining thepush rod cooler than the normal cooling medium temperature during thewarming up period and hotter than the cooling medium under severeconditions of operation and supporting means for the rocker arm shaft,said last mentioned means constituting the sole supporting means forsaid shaft and being formed wholly of material having a substantiallygreater coefiicient of expansion than the other parts whereby the valvelash when the parts are cold is less than the normal hot lash andwhereby the lash under severe conditions of operation is at least equalto normal hot lash.

3. An engine comprising a cylinder having a head, a piston in thecylinder, a valve in the head, operating means for the valve comprisinga rocker arm shaft support mounted on the head, a rocker arm shaftmounted in the support, a rocker mounted on the shaft having one endengaging the valve, a push rod engaging the other end of the rocker, andmeans for operating the push rod to operate the valve, said engine beingprovided with the usual cooling system and lubricating system, and saidrocker ar'in shaft having passages therein, and means for circulatingcooling fluid and lubricating oil from said systems through saidpassages to stabilize the temperature of the shaft and associated partsunder difierent operating conditions, said shaft support being madewholly of material having a higher coefiicient of expansion than theremainder of the valve operating means to maintain the valve lashsubstantially constant throughout the operating range.

JOSEPH D. TURLAY.

